Catalyst for converting paraffinic hydrocarbon into corresponding olefin

ABSTRACT

The invention relates to a calcinated catalyst for converting paraffinic hydrocarbon into corresponding olefin through dehydrogenation. The catalyst is an oxidic, heat-stable carrier material and contains a catalytic active constituent, which is applied on the carrier material and has the following composition (in wt. % in relation to the entire weight of the catalyst): a) 0.2 to 2.0% of at least one element of the groups Pt and Ir and, acting as a promoter, a combination of elements from the six following groups of substances: b) 0.2 to 5.0% of at least one of the following elements Ge, Sn, Pb, Ga, In, Tl; c) 0.1 to 5.0% of at least one of the following elements Li, Na, K, Rb, Cs, Fr; d) 0.2 to 5.0% of at least one of the following elements Fe, Co, Ni, Pd; e) 1.0 to 5.0% P; f) 0.2 to 5.0% of at least one of the following elements Be, Mg, Ca, Sr, Ba, Ra and lanthanides and g) 0.1 to 2.0% Cl.

FIELD OF THE INVENTION

The invention relates to a calcined catalyst for converting paraffinhydrocarbons into corresponding olefins by dehydrogenation, wherein thecatalyst contains an oxidic, thermally stabilized substrate material anda catalytically active component that is applied to the substratematerial. The invention also relates to a method for converting paraffinhydrocarbons into corresponding olefins, in which a stream of theparaffin hydrocarbons is mixed with water vapor and put into contactwith a catalyst. The paraffins addressed within the scope of theinvention are in the range from C₂ to C₂₀, preferably in the range fromC₂ to C₅.

BACKGROUND OF THE INVENTION

A large number of catalysts that are used to dehydrogenate paraffins areknown. Such catalysts have a thermally stabilized, inorganic oxide asthe substrate material, an active component (preferably a metal of theplatinum group), and one or more promoters. Active Al₂O₃, which has anespecially large specific surface area, is often used as the substratematerial.

U.S. Pat. No. 4,788,371, describes a catalyst and a method fordehydrogenating paraffins in a water vapor atmosphere. The substrate ofthe catalyst comprises Al₂O₃ and is coated both with a noble metal(preferably platinum) and several promoters, which are selected fromGroup III or IV of the Periodic table and the gallium or germaniumsubgroup (preferably tin) and alkaline metals (preferably potassium orcesium). The dehydrogenation method described in this reference canfunction in the presence of a limited amount of oxygen, which is used toheat the reaction zone by combusting hydrogen.

From U.S. Pat. No. 5,220,091, a catalyst and a method fordehydrogenating C₂ to C₈ paraffins in the presence of water vapor isknown. The catalyst used here comprises platinum (approximately 0.7weight %) as well as zinc aluminate and potassium aluminate. In thedehydrogenation of isobutane (iC₄), a conversion rate of 50% and aselectivity of 94 mol-% was attained; the pressure was adjusted to P=3.5bar, the temperature was adjusted to T=571° C., and the ratio of steamto isobutane (mol) was adjusted to 3.96. After a cycle time of 7 hours,the catalyst had to be subjected to a reactivation treatment byoxidative regeneration.

A further method and a catalyst for dehydrogenation of organic compoundsis described in European Patent Disclosure EP 0 568 303 A2. This methoduses a hydrogen atmosphere. The catalyst contains nickel and variouspromoters of Groups I-VIII of the Periodic table on a non-acid substratematerial (base-treated Al₂O₃, zeolites, etc.). The special feature ofthe technology described in this reference is many dehydrogenation zoneswith intermediate zones for oxidizing hydrogen produced, on a specialcatalyst. The best results in the dehydrogenation of isobutane wereobtained with a nickel catalyst (3.4% Ni and 3.4% Cr on a Ba-exchangedzeolite L), using a temperature of T=602° C., a molar ratio H₂/iC₄=6 anda space velocity of WHSV=650 h⁻¹. Over an operating duration of 6 hours,the conversion rate was 30-36.6% and the selectivity was 75.1-83.4%. Foran operating duration of 50-65 hours, the conversion rate was in therange from 22.2-27.9% and the selectivity was in the range from78.8-81.1%.

Another catalyst and a method for dehydrogenation of hydrocarbons isknown from International Patent Disclosure WO 94/29021. The methodoperates in a water vapor and hydrogen atmosphere, using a platinumcatalyst, which as promoters contains elements of the tin subgroup andalkaline metals (potassium, cesium). The special feature of the catalystis a special substrate material, which comprises a mixture of magnesiumoxide and aluminum oxide. This composition requires a specialpretreatment of the catalyst, which comprises a reduction with hydrogen,a calcination in an O₂ atmosphere, and another reduction (called an RORtreatment). With this ROR treatment, the catalyst has an activity threetimes higher than without this treatment. The dehydrogenation of propane(C₃) with the aid of the described catalyst, at a temperature of T=600°C., a pressure of P=1 bar, a space velocity WHSV=1.3 h⁻¹ and a ratio ofH₂/H₂O/C₃=0.14/1.2/1 and an operating time of 25 hours, led to thefollowing results: The propylene yield was 55.5 mol-%, and theselectivity was 96.1 mol-%. A comparative test described in thisreference, using a catalyst known from U.S. Pat. No. 4,788,371, underotherwise identical conditions, led to a propylene yield of 25.7 to 29.7mol-% and a selectivity of 95.0 to 95.9 mol-%. Thus WO 94/29021represents the performance standard thus far in the field of catalyticconversion of paraffin hydrocarbons into corresponding olefins.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to disclose a catalyst forconverting paraffin hydrocarbons into corresponding olefins that notonly assures high effectiveness, or in other words has a good conversionrate and good selectivity, but furthermore exhibits high operatingstability; that is, it can be used over comparatively long cycle timesbefore having to be subjected to a reactivation treatment. Theproduction of the catalyst should be as simple as possible. A method forconverting paraffin hydrocarbons into corresponding olefins, which leadsto good olefin yields and can be operated over cycle times that are aslong as possible before catalyst reactivation has to be done is also tobe disclosed.

In terms of the catalyst, this object is attained by the characteristicsrecited in claim 1, and in terms of the method, it is attained by thecharacteristics recited in claim 16. Advantageous features of theinvention are defined by the dependent claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the course of the tests that led to the present invention, it wasdiscovered that catalysts known per se on Al₂O₃ substrates, which haveplatinum, a metal of the germanium or gallium group (preferably tin orindium) and an alkali metal (preferably potassium or cesium) can beimproved substantially in terms of their activity by the addition ofcertain promoters. Along with progress in increasing the catalyticactivity, it can be noted as a particular advantage of the inventionthat no special activation treatment, such as the ROR treatment, isnecessary in the production of the catalyst. Furthermore, in the use ofthe catalyst, there is no need to add hydrogen to the feed material. Onthe contrary, the catalyst functions quite reliably in the presence ofoxygen. The production of the catalyst can be done by known methods onconventional substrate materials.

The calcined catalyst of the invention comprises a thermally stabilizedsubstrate material, onto which a catalytically active component isapplied. The substrate material is preferably aluminum oxide, inparticular in the form of Θ-Al₂O₃. The catalytically active componentcomprises the material groups a) through g), explained in further detailhereinafter, in which the quantities are given in weight % and arereferred to the total weight of the

The material group a) includes the elements Pt and Ir, which representsthe substance that is catalytically effective in the narrower sense,while the other material groups can be considered essentially aspromoters, which promote the catalytic activity. The catalyst must haveat least one of the elements of group a), specifically in a quantity offrom 0.2 to 2%. The element Pt is especially preferred. It isrecommended that the content of the element or elements of materialgroup a) be limited to 0.3 to 0.6%.

As the promoter in the catalyst of the invention, at least one of eachof the elements listed in material groups b) through g) described belowmust be represented. The material group b) comprises the elements Ge,Sn, Pb, Ga, In and Tl. The content of material group b) in the catalystis in the range from 0.2 to 5%, and expediently in the range from 0.5 to2.5%. The use of Sn is especially preferred.

The material group c) includes the elements Li, Na, K, Rb, Cs and Fr andhas a quantitative proportion of from 0.1 to 5%, and preferably 0.5 to1.5%. The elements K and Cs from this material group have proved to beespecially effective.

The material group d) includes the elements Fe, Co, Ni and Pd. Itscontent is in the range from 0.2 to 5%, and preferably in the range from1.0 to 3%. The use of Fe and/or Ni from this material group isespecially expedient.

As a further promoter, the catalyst of the invention has a proportion(e) of P on an order of magnitude of from 1.0 to 5%. It is recommendedthat the P content be limited to from 2.0 to 4.0%. The material groupf), whose quantity is limited to a proportion of from 0.2 to 5% andpreferably to a range from 1.0 to 3%, includes the elements Be, Mg, Ca,Sr, Ba, Ra, and the group comprising the lanthanides. From this group,the elements Ca and Ba are preferred.

Finally, the catalyst has a proportion (g) of Cl on an order ofmagnitude of from 0.1 to 2%. The element Cl is a component that does notact as a promoter in the strict sense of the word, but that improves theinitial dispersion of the noble metal in the catalyst. On the otherhand, Cl promotes undesired secondary reactions at the onset of use ofthe catalyst. The initial content should therefore be clearly limited.

With the present invention, a method for converting paraffinhydrocarbons into corresponding olefins is also proposed in which astream of the paraffin hydrocarbons is mixed with water vapor and putinto contact with a catalyst that has the above-described composition ata temperature in the range from 500 to 650° C. and at a pressure of atleast 1.0 bar (absolute). Expediently, the addition of H₂ to the streamof paraffin hydrocarbons and water vapor that until now was often usualis expediently dispensed with. It is recommended that the molar ratio ofthe water vapor to the paraffin hydrocarbons be adjusted within a rangefrom 0.5:1 to a maximum of 10:1, and preferably within a range from 1:1to 6:1. It has proved to be especially advantageous to use the catalystof the invention with feed materials that contain hydrocarbons of thegroup comprising the C₂ to C₆ paraffins. To improve the conversion, itis advantageous to add O₂ to the stream of paraffin hydrocarbons,because the oxygen reacts with the liberated hydrogen and thus shiftsthe equilibrium of the reaction. A molar ratio of the paraffinhydrocarbons to the O₂ in the range from 1:0.2 to 1:1.5, and inparticular in the range from 1:0.3 to 1:0.7 has proved especiallyexpedient.

The invention will be described in further detail below in terms ofexemplary embodiments.

EXAMPLE 1

To produce a catalyst, 14 g of Θ-Al₂O₃ as the substrate material(specific surface area, 130 m²/g) were impregnated with an aqueoussolution of two salts. This solution was formed from 15 cm³ of waterinto which 2.5 g of potassium nitrate (tetrahydrate) and 0.7 g of nickelnitrate (hexahydrate) were added. The impregnated substrate materialremained at room temperature for 10 hours and was then dried for aduration of 5 hours at 100° C. and for a duration of a further 5 hoursat 150° C. The dry material was then calcined for 2 hours at 350° C. andfor a further 2 hours at 550° C., the rate of the temperature increasebeing approximately 1° C./min.

The material produced in this way was then impregnated withorthophosphoric acid (55 g of 84% phosphoric acid in 18 cm³ of water).After that, the material was dried and re-calcined in the mannerdescribed above. Next, the material was impregnated with tin dichloride(0.29 g of SnCl₂×2H₂O in 20 cm³ of ethanol with the addition of 0.2 g ofconcentrated hydrochloric acid, stirred constantly with slight heatingto up to 40° C.), dried, and again calcined as described above.

After that, this material was impregnated with 18 cm³ of an aqueoussolution of hexachloroplatinic acid (0.093 g of metallic Pt), dried, andcalcined again in the same manner. Finally, the material was impregnatedwith 18 cm³ of an aqueous solution that contained 0.36 g of KNO₃, thendried, and again calcined as described. In this way, a catalyst wasproduced which had the following composition, in weight % referred tothe total weight of the catalyst:

3% Ca 1% Ni 1% P 2% Sn 1% K 0.6%   Pt 0.5%   Cl

This catalyst is listed as catalyst A in Table 1.

EXAMPLE 2

The effectiveness of catalyst A was tested in an experiment lasted 5hours, in which propane was dehydrogenated in a steam atmosphere. Thefollowed values were established as the test conditions:

P = 1 bar T = 550° C. WHSV = 1.2 h⁻¹ H₂O/C₃ = 4.5 (mol)

The resultant conversion rate, selectivity, and propane yield are shownin Table 1.

EXAMPLE 3

In a way corresponding to what is described in Example 1, catalysts B,C, D and E were produced; only the P content was increased in stages to2.0% (B), 2.5% (C), 3.5% (D), and 5.0% (E). The composition of catalystsB through E is shown in Table 1. This table also shows the resultsobtained in an effectiveness test of these catalysts; the testconditions were the same as in Example 2.

EXAMPLE 4

For comparison with the catalysts A through E of the invention, acatalyst F was also produced analogously to the manner described inExample 1, but neither P nor Ca was included in the composition. Thiscatalyst was also tested under the conditions listed in Example 2. Theresults are shown in Table 1.

EXAMPLE 5

As the second comparison example, a catalyst G was produced analogouslyto the manner described in Example 1; it had the same composition ascatalyst B, except that it did contain any Ni. This catalyst G was alsotested under the test conditions of Example 2. The results are shown inTable 1.

EXAMPLE 6

A catalyst H was produced analogously to the manner described; itscomposition differed from catalyst D in that the K content was raised to1.5% and the P content was raised to 3%, and furthermore, instead of 1%Ni, 3.5% Fe was added. The Fe addition was made in the form of anaqueous solution of Fe(NO₃)₃×9H₂O. This catalyst was again tested underthe conditions of Example 2.

The results are shown in Table 1.

EXAMPLE 7

A catalyst K was produced analogously to the manner described; in itscomposition, it differed substantially from catalyst H only in thatinstead of 3.5% Fe, 1% Pd was added. The palladium was added in the formof an aqueous solution of PdCl₂, which contained 3% HCl. Theeffectiveness was again tested under the conditions of Example 2. Theresults are shown in Table 1.

EXAMPLE 8

A catalyst L was produced analogously to the manner described; itdiffered from catalyst D only in that the P content was reduced from3.5% to 3.0%, and instead of 3% Ca, 3% Ce was added. This catalyst wasalso tested under the conditions of Example 2. The results are shown inTable 1.

EXAMPLE 9

A catalyst M was produced in the same way as catalyst B, with the onlydifference that the K content was increased from 1% to 2.2%. Thiscatalyst was also tested under the conditions of Example 2. The resultsare shown in Table 1.

EXAMPLE 10

A catalyst N was produced in the same way as catalyst D, except that theP content was reduced from 3.5% to 3%, and instead of 1% K, 2% Cs wasadded here. The catalyst was again tested under the conditions ofExample 2. The results are shown in Table 1.

EXAMPLE 11

A catalyst R was produced in the same way as catalyst B; the compositiondiffered from the composition of catalyst B only in that instead of 3%Ca, 2% Ba was added here. The barium was added in the form of a nitratein aqueous solution. The catalyst was again tested under the conditionsof Example 2. The results are shown in Table 1.

EXAMPLE 12

Again for comparison with catalysts of the invention, a catalyst S wasmade in the manner described in Example 1, but the elements Ni, Ca and Pwere left out of the composition. The catalyst was again tested underthe conditions of Example 2. The results are shown in Table 1.

It is quite clear from Table 1 that the addition of Ca, Ni and P toplatinum-tin-potassium catalysts known per se causes a quiteconsiderable increase in catalyst activity with regard to thedehydrogenation of paraffins in a steam environment. This is shown bythe catalysts A through E of the invention, for example, in comparisonto the comparison catalyst S. For one skilled in the art, this is acompletely unexpected effect, because the addition of only one of thesecomponents (namely Ni) or only two of these components (namely Ca and P)has a negative influence on the catalyst effectiveness, as the twocatalysts F and G, which are not according to the invention, show incomparison to catalyst S, also not of the invention. Furthermore, itshould be noted that it is widely known that P is a catalyst poison incatalytic dehydrogenation by means of a noble metal catalyst. Table 1,for catalysts H and K, shows that the promoter effect is assured even ifinstead of Ni, a different metal in the iron group (Group VIII), whichis considered a catalyst poison with respect to platinum, or palladiumis used. It can be seen from the example of catalysts L and R thatinstead of calcium, a different alkaline earth metal (such as barium) ora rare earth metal (such as cerium) can also be employed.

EXAMPLE 13

To test the long-term effectiveness, catalysts B, L and S were subjectedto an operation test, in which the same conditions were established asin Example 2. The only difference was that the test duration wasprolonged substantially. The results are shown in Table 2. For thecomparison catalyst S, the test had to be stopped after only about 20hours of operation, because of carbonization.

EXAMPLE 14

Catalysts B and D were also subjected to a long-term test in thedehydrogenation of propane. In contrast to the test conditions ofExample 13, however, the following parameter values were established:

P = 2 bar T = 580° C. WHSV = 1.2 h⁻¹ H₂O/C₃ = 6 (mol)

For catalyst B, the H₂O/C₃ ratio was adjusted to 4 (mol), instead of 6(mol). The results of the two tests are shown in Table 3.

EXAMPLE 15

Catalyst B was tested in an experiment in which over a test duration of5 hours, isobutane was dehydrogenated under the following conditions:

P = 1 bar T = 530-550° C. WHSV = 1.2 h⁻¹ H₂O/iC₄ = 4 (mol)

The results are shown in Table 4.

The advantages of the catalysts of the invention are clearly confirmedby the results of the long-term tests shown in Tables 2 and 3. Theimproved activity and selectivity is exhibited even in thedehydrogenation of other paraffins, such as isobutane. The test resultsshown for this in Table 4 confirm that the catalyst effectiveness in thedehydrogenation of olefins is assured both in a pure water vaporenvironment and when oxygen is added (lower half of the measurementresults in Table 4). In comparison to the known catalysts described atthe outset, the catalyst of the invention also has markedly betteractivity over a longer operating duration, so that the cycle timebetween two reactivation treatments is substantially longer.

TABLE 1 Propylene Composition (weight %) Conversion Selectivity YieldCatalyst a b c d e f g (%) (mol-%) (mol-%) A 0.6 Pt 2 Sn 1 K 1 Ni 1 P 3Ca 0.5 Cl 38 88 33.4 B 0.6 Pt 2 Sn 1 K 1 Ni 2 P 3 Ca 0.5 Cl 44.7 94 42 C0.6 Pt 2 Sn 1 K 1 Ni 2.5 P   3 Ca 0.5 Cl 49 94 46 D 0.6 Pt 2 Sn 1 K 1 Ni3.5 P   3 Ca 0.5 Cl 55.5 91 50.5 E 0.6 Pt 2 Sn 1 K 1 Ni 5 P 3 Ca 0.5 Cl40.0 95 38 F*⁾ 0.6 Pt 2 Sn 1 K 1 Ni — — 0.5 Cl 41.2 68 28 G*⁾ 0.6 Pt 2Sn 1 K — 2 P 3 Ca 0.5 Cl 15.4 91 14 H 0.6 Pt 2 Sn 1.5 K 3.5 Fe 3 P 3 Ca0.5 Cl 52 93 48.4 K 0.6 Pt 2 Sn 1.5 K 1 Pd 3 P 3 Ca  <2 Cl 48 95.5 45.8L 0.6 Pt 2 Sn 1 K 1 Ni 3 P 3 Ce 0.5 Cl 55 89.5 49.2 M 0.6 Pt 2 Sn 2.2 K1 Ni 2 P 3 Ca 0.5 Cl 47.5 92.5 43.9 N 0.6 Pt 2 Sn 2 Cs 1 Ni 3 P 3 Ca 0.5Cl 57 90.5 51.6 R 0.6 Pt 2 Sn 1 K 1 Ni 2 P 2 Ba 0.5 Cl 52 93 48.4 S*⁾0.6 Pt 2 Sn 1 K — — — 0.5 Cl 34 88 30 *⁾Comparison Examples

TABLE 2 Long Term Test P = 1 bar H₂O/C₃ = 4.5 (mol) Duration ofOperation (in hours) WHSV = 1.2 h⁻¹ 5 10 15 20 30 40 50 60 70 80 90 100Catalyst B Temperature (° C.) 550 550 580 580 580 580 580 580 580 580580 590 Conversion (%) 51 54 64 64.5 63.5 62 60 58 58 57 54 57.5Selectivity (mol-%) 91 92 87 88 89 90 90 92 92 92 93 91 Catalyst LTemperature (° C.) 550 550 550 550 550 550 550 550 550 550 550 550Conversion (%) 56 56 56 56 55 55 55 55 55 54 54 54 Selectivity (mol-%)90 91 91 92 93 93 93 94 94 95 95 95 Catalyst S Temperature (° C.) 550560 570 580 Conversion (%) 34 36 38 40 Selectivity (mol-%) 89 87 86 85

TABLE 3 Long Term Test P = 2 bar Duration of Operation (in hours) WHSV =1.2 h⁻¹ 5 10 20 30 40 50 60 70 80 90 100 Catalyst B Temperature (° C.)580 580 580 580 580 580 580 580 580 590 590 H₂O/C₃ = 6 (mol) Conversion(%) 57 56 56 55 55 54 53 51 50 52 50 Selectivity (weight %) 85 86 86 8788 88 89 89 89 88 88 Propylene Yield 48.5 48 48 48 48.5 47.5 47 45.544.5 46 44 (weight %) Catalyst D Temperature (° C.) 580 580 580 580 580580 580 580 600 600 600 H₂O/C₃ = 4 (mol) Conversion (%) 55 56 56 54 5353 52 50 57 53 50 Selectivity (weight %) 85 86 86 88 90 90 90 91 89 8990 Propylene Yield 47 48 48 47.5 47.5 47.5 47 45.5 50.5 47 45 (weight %)

TABLE 4 Isobutylene Temperature O₂ Content Conversion Selectivity Yield(° C.) in Feed Material (%) (mol-%) (mol-%) 530 None 59 96.5 56.9 540None 61.5 96 59 550 None 63.5 96 61 550 0.4 66.5 96 62.8 550 0.7 66 9462 550 1.4 66 93 61.4

We claim:
 1. A calcined catalyst for converting paraffin hydrocarbonsinto corresponding olefins by dehydrogenation, wherein the catalystcontains an oxidic, thermally stabilized substrate material and acatalytically active component that is applied to the substrate materialand has the following composition (in weight % of the total weight ofthe catalyst): a) from 0.2 to 2.0% of at least one of the elements ofthe group comprising Pt and Ir, and as a promoter a combination ofelements of each of the following six material groups: b) from 0.2 to5.0% of at least one of the elements Ge, Sn, Pb, Ga, In, and Tl, c) from0.1 to 5.0% of at least one of the elements Li, Na, K, Rb, Cs, and Fr,d) from 0.2 to 5.0% of at least one of the elements Fe, Co, Ni, and Pd,e) from 1.0 to 5.0% of P, f) from 0.2 to 5% of at least one of theelements Be, Mg, Ca, Sr, Ba, Ra and the lanthanides, g) from 0.1 to 2%Cl.
 2. The catalyst of claim 1, characterized in that the substratematerial is Al₂O₃.
 3. The catalyst of claim 1, characterized in that thecontent of the elements of material group a) is limited to from 0.3 to0.6%.
 4. The catalyst of claim 1, characterized in that the content ofthe elements of material group b) is limited to from 0.5 to 2.5%.
 5. Thecatalyst of claim 1, characterized in that the content of the elementsof material group c) is limited to from 0.5 to 1.5%.
 6. The catalyst ofclaim 1, characterized in that the content of the elements of materialgroup d) is limited to from 1.0 to 3.0%.
 7. The catalyst of claim 1,characterized in that the P content is limited to from 2.0 to 4.0%. 8.The catalyst of claim 1, characterized in that the content of theelements of material group f) is limited to from 1.0 to 3.0%.
 9. Thecatalyst of claim 1, characterized in that Pt is selected as the elementfrom group a).
 10. The catalyst of claim 1, characterized in that Sn isselected as the element from group b).
 11. The catalyst of claim 1,characterized in that K is selected as the element from group c). 12.The catalyst of claim 1, characterized in that Cs is selected as theelement from group c).
 13. The catalyst of claim 1, characterized inthat Fe and/or Ni is selected as the element from group d).
 14. Thecatalyst of claim 1, characterized in that Ca is selected as the elementfrom group f).
 15. The catalyst of claim 1, characterized in that Ba isselected as the element from group f).
 16. A method for convertingparaffin hydrocarbons into corresponding olefins, in which a stream ofthe paraffin hydrocarbons is mixed with water vapor and put into contactwith a catalyst of claim 1 at a temperature in the range from 500 to650° C. and at a pressure of at least 1.0 bar (absolute).
 17. The methodof claim 16, characterized in that the stream of paraffin hydrocarbonsand the water vapor are free of a H₂.
 18. The method of claim 16,characterized in that the molar ratio of the water vapor to the paraffinhydrocarbons is at least 0.5:1.
 19. The method of claim 16,characterized in that the molar ratio of the water vapor to the paraffinhydrocarbons is limited to a maximum of 10:1.
 20. The method of claim16, characterized in that the molar ratio of the water vapor to theparaffin hydrocarbons is in the range from 1:1 to 6:1.
 21. The method ofclaim 16, characterized in that the hydrocarbons belong the group of C₂to C₆ paraffins.
 22. The method of claim 16, characterized in that O₂ isadded to the stream of paraffin hydrocarbons.
 23. The method of claim22, characterized in that the molar ratio of the paraffin hydrocarbonsto the O₂ is in range from 1:0.2 to 1:0.5.
 24. The method of claim 23,characterized in that the molar ratio of the paraffin hydrocarbons tothe O₂ is in range from 1:0.3 to 1:0.7.
 25. The catalyst of claim 2,wherein the substrate material is Θ-Al₂O₃.